Mobil networks, such as mobile networks for cellular telephones, comprise sending stations which are distributed over the landscape. Each sending station is attributed to one “radio cell”, and in turn, a “cell code” is attributed to each radio cell. Certain values relevant for the planning and the function of the radio cell vary across the area of the radio cell, such as, for example, the “path loss data”. These characterize the physically based radio propagation fading. The receiving power of an end device, for example a cellular telephone, decreases with increasing distance from the sending station for a given sending power of a sending station emitted in a given direction. This decrease is caused, on one hand, by the distribution of the emitted sending power to a wave front area increasing with the distance similar as it is the case with light. The decrease, however, is also determined by absorption or buildings or the topography of the landscape.
For the planning and optimizing of a radio network radio network models are generated. For this purpose the area of a radio cell is divided into a pattern of relatively small area portions. “Model values” are attributed to each of these area portions. They are the values of a variable relevant for the function of the mobile network valid for this area portion. Such a variable is, in particular, the path losses. It can also be that the sending power is received by a sending station with different intensities and running times at a certain point of a radio cell. An impulse-shaped sending signal is then received in the form of several time-delayed impulses with different height. This is called “impulse response”. The values of such a model variable attributed to the individual area portions form a matrix.
In the planning phase, i.e. before installing the radio network, relevant physical values cannot be measured. After the installation of the radio network it is also not possible to measure such physical values, such as the path losses for each individual area portion. Most of the area portions are not accessible without problems. Furthermore, the efforts and expenses for such measurements in each area portion are extremely high. Therefore mathematical models for predicting a radio channel have been developed, modelling the various influencing variables and their influence on, for example, the path losses due to physical rules or empirically found relationships. These models comprise certain parameters.
The channel models obtained in such a way usually do not properly fit to the reality. It is, therefore, necessary to adapt the channel models obtained at first to the reality as well as possible using measured data of real variables. For this purpose the parameters of the channel models in known methods are varied based on measured data. The parameters and terms of the channel models are adapted step-by-step and the values for the path losses repeatedly newly calculated. This method takes a lot of efforts, because it is not known which parameter is responsible in which way of the deviations between the measured values and the model values, i.e. how the parameters must be varied to minimize the deviations between the model and the reality.
An example for this prior art is the publication by D. J. Y Lee and W. C. Y Lee “Fine Tune Lee Model”, p. 406-410 IEE Conference on Personal, Indor and Mobile Radio Communications” 18-21 Sep. 2000.
From WO 02/073997 A1 a method for adapting a path loss model to the conditions of a real radio network is known wherein at first a path loss model is obtained at measuring positions from the information about a base station, that is the sending power, emitting pattern and height, topographical information and measured data, i.e. signal strength. The model obtained from physical conditions is supported by real measured data. The measured data influences, as described above, are the parameters of the model. Such a path loss model provides a model value in the form of a path loss value for each point of the considered sending area. Normally, deviations of the path loss values obtained from the model from the real measured data occur. Such deviations occur due to shading. To take such shading into account this shading is statistically evaluated in a further step providing parameters for a shading prediction in the considered area. Thereby a second model is used for the shading, the parameters of which are determined from the deviations of the measured data from the path loss values obtained from the first model. The shading values obtained in such a way are superimposed on the path loss values obtained from the first model. If the measured values are very reliable, the path loss values obtained from these models at the measuring positions can be substituted by real measured data. For smaller reliability of the measured values a weighted average value of the measured data and model values is used instead of the measured values.
The method according to the WO 02/073997 A1 therefore operates with two models in two steps, the parameters of the models being determined using measured data which have been obtained at certain measuring positions. Therefore, this is also the determination of parameters of models as it is the case with the previously mentioned prior art. The substitution of the model values by real measured data is effected, if at all, at the measuring positions themselves.